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Full text of "Alaskan glacier studies of the National Geographic Society in the Yakutat Bay, Prince William Sound and lower Copper River regions"

evidence was so clear that it is brought out distinctly in the photographs taken from the earlier sites. From Gilbert's site, for instance, at an elevation of 1000 feet on the mountain slope above Osier Island, it was clearly evident that the northwestern arm had continued to advance since 1906, the extreme western margin being several hundred yards farther out and the ice cliff in that part of the glacier being slightly extended. One of the evidences of advance of the northwest arm discovered in 1905 was changed, namely, the position of the bend of the medial moraine of that arm. This bend was further back, and where deflected westward, the curve was blunter than in 1905. This might be due either to increase in weakness of the northwest arm or to increase in strength of movement of the north arm. That it is not the former is proved by the continued advance of the western margin of the Hubbard. This leads to the acceptance of the latter interpretation, and direct proof of its correctness is supplied by the condition of the southeastern part of the glacier. The extreme outermost part of the ice front, which is supplied from the north arm, projected 200 or 300 feet farther out than in 1906 and at least a quarter of a mile farther than in 1891. Along the southeastern margin there was much less de"bris than in 1905 and 1906 and the eastern portion of the ice cliff had a far larger proportion of clear ice. A further noteworthy fact was the position of a moraimc ribbon that lay on the glacier just outside of the southeastern lateral moraine. In 1906 it was much farther out in the glacier than in 1909 as if in the meantime it had been pushed westward, in toward the valley wall by the advance of the glacier.
All these facts convince us that while the northwest arm had advanced somewhat, the north arm had also begun an advance in the interval between 1906 and 1909. There was quite certainly a much more active discharge of ice from the glacier front than in 1905 and 1906. Sometimes there was an almost steady roar for a half hour. There was very heavy ice off the glacier front, far more than in former years, though it is of course true that this condition varies greatly from time to time. The natives report such heavy ice in 1909 as to interfere with their Baling. Neither in 1905 nor 1906 was there nearly so much stranded ice on the beach at our camp site on the west shore of the bay as in 1909. It seemed certain that the forward thrust of the ice front, which was unquestionably in progress, was accompanied by a more rapid discharge of ice into the fiord.
Clear and convincing proof of recent advance was found at the southeastern margin of the Hubbard Glacier. There was certainly a considerable advance of the front as viewed from the photographic sites selected by Gilbert in 1899 and re-occupied (approximately) by us in 1905 and 1906; but since these sites are on the beach we cannot be certain that we re-occupied them exactly, and accordingly, in 1909, we established a new photographic station (F. Map 8) on a neighboring morainic mound, marking its site by a cairn.
The clearest evidence of advance of the southeastern margin, however, is furnished by the change in the condition of the glacier itself. The ice cliff, which extends here from the land into the sea was much more broken than formerly, it had a much smaller proportion of debris-stained ice, and there were frequent falls of icebergs from its face. In former years only small blocks fell from this front, and then only rarely, but during the period of our observation in 1909 there were many ice falls, some of them of large size. This indicated that the stagnant margin was advancing and there was abundant further proof of this conclusion in the change in condition of the margin where it rested on the land nearby. In 1906 and previous years this margin was a uniformly debris-covered